The cover is only part of it. How was it kept by this owner before the custom cover or the previois owner?
W out seeing pix, and deciding based on them if its worth a drive, then seeing it in person, IMO, all 30yr old boats have suspect waterlogged foam.
If the transom is compromised, water has gotten below decks, just a matter of how much.
After countless prospects, I'd think it woud have become more obvious: but w little info initially, no pix and no link to the ad, its nearly impossible to recommend buying the boats you post topics about, or even recommend whether they are worth the drive to go see, 10miles away or 10hours away...
If the sellers cant be bothered to provide lots of info (you should now have a long list of typical questions to ask) or provide pix, then I'd suggest they dont really want to sell their boat, sooner rather then later.
Or invest your time and effort to go see the boats, assess them for yourself and take your own pix. Bring that assessment and your pix back, start a topic and ask for opinions based on info you gathered.